Presented here is the synthesis of three new Schiff-base cryptands, 4–6. Dynamic covalent imine bond formation via the condensation of a dialdehyde (7 or 8) with two different tris-amines allowed for the preparation of 4–6 in 84%, 80% and 83% yield, respectively. These systems were characterized by NMR spectroscopy, mass spectra, and, in the case of 5, single crystal X-ray diffraction analysis. These cages act as selective CO[Formula: see text] gas adsorbing materials in the solid state.